She had a thin build with lavender fur, her horn and ears ending at a point. Her mane and tail, seagreens, turquoises and blues like the mist of the mountains, flowed on behind her in a river current, just like that of Celestia and Luna. Her hooves faded from lavender to a cream white, and on her flank, a Cutie Mark of a seagreen cloud. It is said she is more beautiful than a Kirin, who're naturally more beautiful than ponies.
Mistmane is a talented sorceress renowned for her beauty and kindness. The love and attention she gets from her friends and family causes her best friend, Sable Spirit, to become jealous. While Mistmane is away at magic school, Sable casts a spell to make herself beautiful, but it backfires and makes her hideous instead. As a result, she decides to take beauty away from everyone and everything else, becoming empress and leading the village into a state of decline.
When Mistmane returns home and finds her friends suffering, she confronts Sable Spirit on her oppression and challenges her to a magic duel, eventually defeating her. Wanting to do more for her friend, Mistmane casts a spell that restores Sable and the village's beauty while sacrificing her own. Sable, moved by her friend's sacrifice, rules with kindness and compassion from then on, and Mistmane dedicates her life to spreading beauty throughout Equestria.
She returns to present day after the Harmony Gems bring them back, and she joins the others in fighting the Pony of shadows to put him back into Limbo.
My Little Universe II
She briefly appears as part of the Pillars during the three-part finale, fighting Grogar's Army in the Realm of Corners.